1. Field of the Invention
This invention relates in general to computer-implemented database management systems, and, in particular, to creating a custom digital library using a system description to describe data in the digital library and a code generator to generate programs which store and locate data in the digital library based on the system specification.
2. Description of Related Art
For nearly half a century computers have been used by businesses to manage information such as numbers and text, mainly in the form of coded data. However, business data represents only a small part of the world's information. As storage, communication and information processing technologies advance, and as their costs come down, it becomes more feasible to digitize other various types of data, store large volumes of it, and be able to distribute it on demand to users at their place of business or home.
New digitization technologies have emerged in the last decade to digitize images, audio, and video, giving birth to a new type of digital multimedia information. These multimedia objects are quite different from the business data that computers managed in the past, and often require more advanced information management system infrastructures with new capabilities. Such systems are often called “digital libraries.”
Bringing new digital technologies can do much more than just replace physical objects with their electronic representation. It enables instant access to information; supports fast, accurate, and powerful search mechanisms; provides, new “experiential” (i.e. virtual reality) user interfaces; and implements new ways of protecting the rights of information owners. These properties make digital library solutions even more attractive and acceptable not only to corporate IS organizations, but to the information owners, publishers and service providers.
Generally, business data is created by a business process (an airline ticket reservation, a deposit at the bank, and a claim processing at an insurance company are examples). Most of these processes have been automated by computers and produce business data in digital form (text and numbers). Therefore it is usually structured coded data. Multimedia data, on the contrary, cannot be fully pre-structured (its use is not fully predictable) because it is the result of the creation of a human being or the digitization of an object of the real world (x-rays, geophysical mapping, etc.) rather than a computer algorithm.
The average size of business data in digital form is relatively small. A banking record—including a customers name, address, phone number, account number, balance, etc.—represents at most a few hundred characters, i.e. few hundreds/thousands of bits. The digitization of multimedia information (image, audio, video) produces a large set of bits called an “object” or “blobs” (Binary Large Objects). For example, a digitized image of the parchments from the Vatican Library takes as much as the equivalent of 30 million characters (30 MB) to be stored. The digitization of a movie, even after compression, may take as much as the equivalent of several billions of characters (3-4 GB) to be stored.
Multimedia information is typically stored as much larger objects, ever increasing in quantity and therefore requiring special storage mechanisms. Classical business computer systems have not been designed to directly store such large objects. Specialized storage technologies may be required for certain types of information, e.g. media streamers for video or music. Because certain multimedia information needs to be preserved “forever” it also requires special storage management functions providing automated back-up and migration to new storage technologies as they become available and as old technologies become obsolete.
Finally, for performance reasons, the multimedia data is often placed in the proximity of the users with the system supporting multiple distributed object servers. This often requires a logical separation between applications, indices, and data to ensure independence from any changes in the location of the data.
In a digital library (DL), the multimedia object can be linked with the associated indexing information, since both are available in digital form. Integration of this legacy catalog information with the digitized object is crucial and is one of the great advantages of digital library technology. Different types of objects can be categorized differently as appropriate for each object type. Existing standards like MARC records for libraries, Finding Aids for archiving of special collections, etc. can be used when appropriate.
Object-oriented approaches are generally better suited for such complex data management. The term “object-oriented” refers to a software design method which uses “classes” and “objects” to model abstract or real objects. An “object” is the main building block of object-oriented programming, and is a programming unit which has both data and functionality (i.e., “methods”). A “class” defines the implementation of a particular kind of object, the variables and methods it uses, and the parent class it belongs to.
When a customer-specific database is to be built, it is usually necessary to interview the customer regarding the content of the database. Then, the objects corresponding to the customer's needs are hard coded to build the specified database. In other words, programming code is generated for each kind of object of the database that was specified by the customer. By hard coding objects, the objects are stored in a predefined scheme based on the type of object.
There are a number of obvious shortcomings with this approach. First, hard coding individual databases requires significant time and money. For example, when new objects are to be added to the library, new code must be written to represent these objects. Similarly, when objects are altered or deleted, the database must be altered and reindexed. This process results in a very inefficient technique for generating custom databases. These shortcomings are further amplified when large, customer specified databases with large objects and/or a large number of objects are to be created. Consequently, the conventional, manual technique for hard-coded systems is inefficient and is not desirable for databases which may require numerous object modifications and additions within a digital library.
Further, other conventional systems which utilize code generators based on static or dynamic code generators also have shortcomings. For example, with code generators based on embedded static-SQL, code must still be written for each individual object, each added object, and each changed object. Further, for each new type of database request, a separate programming language function must be created. In addition, conventional dynamic embedded-SQL code generators do not perform as well as static embedded-SQL code generators and are generally directed to small databases rather than larger databases or custom databases.
Accordingly, there is a need in the art for a system that can create and manage custom databases using a search engine that is capable of efficient, run-time storing and locating of data within the database without generating new code, modifying existing code, or reindexing a database to reflect the addition, deletion or alteration of an object within a database.